Pulse generating circuits



June 26, 1956 H. B. DE VORE 2,752,487

PULSE GENERATING CIRCUITS Filed Sept. 7, 1950 9 Val 7:465 PUWFRJUPPZY 222.5K- V.

a! was Pew/914:2 10/?) I Hunk/v7 I ATTORNEY United States Patent" 2,7'5i,48'7 PULSE GENERATING emeulrs Henfy B, De Vere, flare Meade,assignor to lt adio Corporation of America, a corporation of'DlawareAp'plifiafidn September 7,195'0', Serial N62"'1 83,'5 8 1 means; (of;i56 27 sifi i v va'ls betweenpiilses1 n I I It is comparatively si -leto" generate negative voltage- P i i. l e a v t afik i -a. 'wrtimr tlanqload. convenient method, employs a vacuum discharge th three or moreelements. Thejload is placed ode circuit; the? cathode is effectivelygrounded; H .control" 'ler'nent is' biased negatively to or beyond on vif thequie'sjcen'tsta'te, Then comparatively small positive voltagepulse drives'the co rftrol elementsulficiently to cause the tube' t6conduct, whereuponthe-anode current, flowing through the anodeload-impedance, develo'ps ai'l'a'r'ge' negat ve voltageipulse, I I

when a positive voltage pulse is required, there are two V f d L I n onecase, a ga iye voltage pulse is deye opedin a manner suchas"describedhereinbefore,- and.this pulse is-fed through ap'olarity rers'ing pulse transformer ofappropriatedesign. This line transformerthat permit of both rapid'voltage riseat the sartof the pulse and asustained voltage amplitude: sinillfdroop) duringthe pplsetirne, Thesecond method is similar to that described for negativepulse generation,In this case, however, the controlrelerne nt is maintainedsubstantiallyat cathode potential during the quiescent state between pulses. Thepulse is'-then gener ate'd applying a' comparatively small =11egativepulsef to the control element, cutting off the current flow armeload,since the rise-occurswith a time: constant'that is" the product of thisresistance" and the: associated circuit 'gu r ed thijs smallloadresistor will necessarily coil"- sunie a large amount of power duringthequiesceiit period; this power being; given-by the equation P= V lRwhere I voltage drop acrossthe? load resistor iii" the quiescentstate,This voltage (V) will beat leasta's' great as the pulse voltage.

Briefly, the present invention consists-of two vacuuni k fi t st s tsis, Se es; ith: ac t andl with a resistor therebetween, the two tubesbeing connectedacrbss terminals of voltage po wensupply; The; re=- sistor between the two tubes furnishes a negative bias potential to egridjof the, pqwei tube. (the t ube nearer tuhe (thethbb nearer 'th grvoltage' p ower supply) is oif by' 'a a N 7 pulse; the currentth'r'oii'ghthe resistor'betwen th tiibes" v d issat isfactory for veryshort-pulses butif a long' pulse is desired, it becomesimpossible todesigna acitaiices. However, when a large: voltage: pulse: is"

" ice 2-v stopsand the potential of; the grid of the power tub'e rapidlyrises to the potential of its cathode and the pedah'ce of thepower tuberapidly decreasesto every small value. The potential of the cathode ofthe'po'wer tube thereby rapidly rises and approaches the potential ofthe positive side of the voltage power supply. This voltage of thecathode of the power tube is coupled to a: load circuit by a capacitor;

Two embodimentsof the invention are disclosed. In one embodiment; theresistor is of the conventional re sistance type and in the otherembodiment the resistorbetween the control and the power tube isthecombination of a conventional resistor and a vacuum' tube referred to asa biastube, The control tube end of ther sistbr is connected to the gridof the bias tube and the other end of the'resis tor is connected to thecathode of the" bias tube and to the grid ofthe power tube;

There is thus provided a very high impedance through the power tubeduring the quiescent stateof the circuit;- that is, betweenpulses,an'd'avery low impedance-through the power tube during pulses.-The circuit, therefore, operates with high economy of power. I

F.urther-more,- astheimpedance through the power tube during pulses-isof very low value, the'time constant at the circuit is very' low andthevoltagerise rate is high Inprac'tice, a rate of voltage rise as high as5X 10 volts per second has been obtained with a loa'd of LOOOohms.

It is known inthe art that two vacuum tubes may be connected in' serieswith a' resistor therebetwee'n, the re: sis tor providing a controlvoltage for one of the tubes.- Eor examples, seeArtzt Patent No.2,310,342 and Blifz Patent No. 2,438,960 This arrangement" of tubes wasused inbalancedamplifiersandreqiiired, for their (spare tion, twoequalresistors in series across-the voltage power supply in ordertoestablish areference riiid volta'ge' foint between the) terminalsof afluctuating voltage power supply. 'Ihisreference midvoltage point servedas one terminal of the output circuit; Also, fo'r operation, a

resistance is used between one'tube and the positive side;

o f the-voltage power supply'which'bears a functional relation totheresistance of the two equal resistors across' the' voltage'power supply.The pr'seritinvention is devoid of these interrelated resistors andtheir relation to the niiilvoltage point in the voltage power supply.

The principal object ofthe invention is to" provide an: improved circuitfor generating? high positive voltage: pulses in which a vacunmtube;functioning'as a-plateloadi for a second vacuum tube, presents a highimpedance be tween pulses antl alow impedance during pulses.

Another object of the invention is to" provide such a;

circuitthat produces a high rate of voltage rise. Another object oftheinvention isto" provide such a' circuit in which the high-positivevoltage'may be sustained over apulse of long duration&

Further objects and advantages of the invention will be apparent fromthe following description" made with" reference to the accompanyingdrawings in which:

Figure l is ascheniati'c diagram'of one embodiment-er;

the inventionin Whicha conventionalresistor is connected between thecontrol tube and the powertiibe;

Eigure 2' is -a-s'chematic diagram of ahbthe'rehibodihient of theinvention in which a conventional resistor and a: bias" Referring'toFigured; 1 is a vacuum mue-fia'viaganode may be noted that the cathodeof tube 1 is connected substantially to ground because of the smallimpedance of resistor 6. This resistor is only for the purpose ofproviding bias to reduce anode current flow between applied pulses andfor some tube type preferably is omitted. Grid 3 is grounded throughresistor 7. Capacitor 8 provides the coupling of tube 1 to a drivingsource, applied at terminals 9, furnishing a negative voltage pulse ofthe desired width. Tube 1 is designated a control tube.

Vacuum tube 10, having an anode 11, grid 12 and cathode 13, is connectedin series with tube 1 through resistor 14, that is, cathode 13 of tube10 is connected to one end of resistor 14 and anode 2 of tube 1 isconnected to the other end of resistor 14. The anode 11 of tube 10 isconnected to the positive side of the voltage power supply at 15. Theend of resistor 14 nearer tube 1 is connected to grid 12 of tube 10.

The voltage of the generated pulse is available at cathode 13 of tube 10and is applied to a load circuit, repre sented by resistor 16, throughcoupling capacitor 17. Tube 10 is designated a power tube.

In the quiescent state, tube 1 is conducting. The current through tube 1passes through tube 11 and resistor 14 and develops a difierence inpotential across resistor 14. This difference of potential is appliedbetween grid 12 and cathode 13 of tube 10 by connecting the end of theresistor nearer tube 1 to grid 12. The potential thus applied to grid 12limits the flow of current through tube 10 to a very small value andcauses most of the voltage drop between the anode supply connection 15and ground to occur within tube 10. Cathode 13 in tube 10 is, therefore,maintained at a low potential.

When a negative voltage pulse is applied to grid 3 in tube 1, tube 1 iscut oil and no current will flow through resistor 14. The potential ongrid 12 in tube 10 thereupon rises quickly to the potential of cathode13 of tube 10. Tube 10 then can pass large currents and hence thepotential of cathode 13 and also grid 12 rapidly rise toward the supplyvoltage at anode 11 of tube 10.

The pulse voltage rise rate is very rapid as this rate is determined bythe capacitance of the load circuit and the very low internal impedanceof tube 11 It is apparent that the power consumed between pulses iscomparatively low as the internal impedance of tube 10 is very high whenits grid 12 is biased negatively with respect to its cathode 13.

In testing the circuit in Figure 1, it was found that the rate ofvoltage rise at the start of the pulse is determined by the magnitude ofthe resistance in resistor 14 and the internal capacitance between grid12 and anode 11 and cathode 13. The effect of resistor 14 and theinternal capacitance of the tube could not be decreased indefinitely,except by reducing the value of the resistance of re sistor 14. However,with this decrease in resistance of resistor 14, the currents flowingduring the quiescent state became larger. Accordingly, there issubstituted for resistor 14 the combination of a resistor and a biastube, the circuits of which are set forth in Figure 2.

Referring to Figure 2, the circuits of the control tube 1 are the sameas in Figure 1. In Figure 2, one end of resistor 14 is connected to theanode 2 of tube 1 and to the grid 18 of a bias vacuum tube 19. The otherend of resistor 14 is connected to cathode 20 of tube 19 and to the grid12 of tube 10. Anode 21 of tube 19 is connected to the cathode 13 oftube 10. Anode 11 of tube 10 is connected at 15 to the positive side ofa voltage power supply.

The voltage of the generated pulse is available at the cathode 13 oftube 10 and is applied to a load circuit, represented by resistor 16,through coupling capacitor 17.

The operation of the circuits in Figure 2 is substantially the same asthe circuits in Figure 1, except that the currents flowing in resistor14, when the control tube 1 is conducting, create a diiference ofpotential across the grid 18 and cathode 20 of the bias tube 19 and thetube i 19 becomes a high impedance cathode resistance for tube 10. Asthe cathode 13 of tube 10 is connected to the anode 21 of tube 19, andas the cathode 20 of tube 19 is connected to grid 12 of tube 19, thepotential between grid 12 and cathode 13 of tube 10 is proportional tothe internal impedance of tube 19. Hence the internal impedance of tube10 is correspondingly high.

The rate of voltage rise at the start of a pulse in the circuits inFigure 2 is greater than that in the circuits in Figure l as thepotential across the bias tube 19 is never very large and hence itscut-off bias is correspondingly low, which permits a small value ofcathode resistance 14. The limitation to the rate of voltage rise in thecircuit in Figure 2 is determined by a time constant which is theproduct of the resistance 14 by the capacitance between grid 1$ and theother elements of tube 19. Since resistor 14 can be much smaller than inthe case of the circuit in Figure 1, this time constant can be made muchsmaller and hence the rate of voltage rise much greater.

In some cases, such as when increased voltage sensitivity is desired,tetrodes or pentodes may be used rather than the triodes in Figures 1and 2. In Figure 3 are the circuits using two 4E27 tubes in parallel, a829B tube both sections in parallel, and a 807 tube. Suitable values ofthe resistances and capacitances in ohms and microfarads are given inFigure 3 for such a combination of tubes, merely by way of example. Withthe given values of the various elements of the circuit and theoperations described hereinbefore of the circuits in Figures 1 and 2,the operation of the circuits in Figure 3 will be obvious to thoseskilled in the art.

What I claim as my invention is:

l. A circuit for producing positive voltage pulses comprising a powertube having a cathode, an anode and a control grid, a control tubehaving a cathode, an anode and a control grid, the cathode of the powertube being connected to the anode of the control tube through animpedance device, the control grid of the power tube being connectedthrough a direct current connection to the anode end of said device, thecathode of the control tube being connected substantially directly toground, in operation a direct current voltage being connected betweenthe anode of the power tube and the cathode of the control tube in thedirection to put positive voltage on the anode of the power tube and inoperation the only current flowing through said impedance device beingcurrent flowing through said power tube, said current acting to providethe sole biasing voltage applied to the control grid of said power tube,and means provided to capacitively connect a load between the cathode ofthe power tube and ground whereby a positive voltage pulse is suppliedfrom the power tube cathode to said load in response to the applicationof a negative voltage pulse to the control grid of said control tube.

2. A circuit for producing positive voltage pulses comprising a powertube having a cathode, an anode and a control grid, a control tubehaving a cathode, an anode and a control grid, the cathode of the powertube being connected to the anode of the control tube through aresistor, the control grid of the power tube being connected through adirect current connection to the anode end of said resistor, the cathodeof the control tube being connected substantially directly to ground, inoperation a direct current voltage being connected between the anode ofthe power tube and the cathode of the control tube in the direction toput positive voltage on the anode of the power tube and in operation theonly current flowing through said impedance device being current flowingthrough said power tube, said current acting to provide the sole biasingvoltage applied to the control grid of said power tube, and meansprovided to capacitively connect a load between the cathode of the powertube and ground whereby a positive voltage pulse is supplied from thepower tube cathode to said load in response to: the application of anegative voltage pulse toithe. control grid. of said. control tube;

3". A circuit for producing. positive: electrical pulses comprising: apower tube having a cathode, as time and a control grid, a. control.tube havirig' a catlibdaan anode and a control grid,:a-. bias tubehaving a cathode, an anode and aco a 'g'rid, s a id tub'es beingconnected together" incathode to aiibde r latioiiwliereby lth rhea;-cathode impedances of said tubes are'ifi s'eiiesrelation; an impedancedevice of comparatively small impedance connecting the cathode of saidbias tube to the anode of said control tube, the control grid of saidbias tube being connected to the anode end of said impedance device, thecontrol grid of said power tube being connected to the cathode end ofsaid impedance device, in operation a direct current operating voltagebeing applied between the anode of said power tube and the cathode ofsaid control tube in the direction to put positive voltage on the anodeof the power tube and means for taking a positive voltage pulse from thecathode of said power tube in response to the application of a negativevoltage pulse to the control grid of said control tube.

4. A circuit for producing positive electrical pulses comprising a powertube having a cathode, an anode and a control grid, a control tubehaving a cathode, an anode and a control grid, a bias tube having acathode, an anode and a control grid, said tubes being connectedtogether in cathode to anode relation whereby the anodecathodeimpedances of said tubes are in series relation, a resistor ofcomparatively small impedance connecting the cathode of said bias tubeto the anode of said control tube, the control grid of said bias tubebeing connected to the anode end of said resistor, the control grid ofsaid power tube being connected to the cathode end of said resistor, inoperation a direct current operating voltage being applied between theanode of said power tube and the cathode of said control tube in thedirection to put positive voltage on the anode of the power tube andmeans for taking a positive voltage pulse from the cathode of said powertube in response to the application of a negative voltage pulse to thecontrol grid of said control tube.

5. In combination: a control tube, a power tube and a bias tube, each ofsaid tubes having, respectively, an anode, a cathode and a grid; asource of negative voltage pulses connected to said control tube; avoltage power supply, the positive side of which is connected to theanode of said power tube and the negative side of which is connected tothe cathode of said control tube; an output pulse load connected to saidpower tube, and a resistor connected at one of its ends to the anode ofsaid control tube and to the grid of said bias tube and at the other ofits ends to the grid of the said power tube and the cathode of the saidbias tube.

6. In combination: a control tube, a power tube and a bias tube, each ofsaid tubes having, respectively, an anode, a cathode and a grid; asource of negative voltage pulses connected to said control tube; avoltage power supply the positive side of which is connected to saidpower tube and the negative side of which is connected to the cathode ofsaid control tube; and output pulse load; means for connecting said loadto said power tube; and a resistor connected at one of its ends to theanode of said control tube and to the grid of the said bias tube and atthe other of its ends to the grid of the said power tube and the cathodeof the said bias tube.

7. In combination: a control tube, a power tube and a bias tube, each ofsaid tubes having, respectively, an anode, a cathode and a grid; asource of negative voltage pulses connected to said control tube; avoltage power supply the positive side of which is connected to saidpower tube and the negative side of which is connected to the cathode ofsaid control tube; an output pulse load connected to the cathode of saidpower tube and to the negative side of said power supply, and a resistorconneeted at one or ends to the anode or said control tube and to thegrid 'of the": said bia's tube" and" at are other of its ends to thegridof the said power tube and the catfiede of s" d bia s t ub i 8. Apulse? generating circuit? comprising, in combination, first, second andthird discharge devices connected 1n the ordffiafirea; ina'riodelto-cathoderelation, of said'fir'stidifscli rge device defining.one end x sci'r'ciii'tandtlie anode o frsaid third discharge devicedefining 'tli'eot h'er e'ridof said series circuit; means for,connecting said'c'atliod eifd to a.so;urce of' reference vbltageiniea'ri's forco'rinectiifgsaid anode end to a source of voltage which ispositive with respect to said reference voltage and of suflicientamplitude to cause current flow through said series circuit; connectionmeans for the cathode of said third discharge device for capacitivelycoupling said cathode through a load to said source of referencevoltage; and means responsive to the current flow through said seriescircuit, when in operation, for biasing said second and third dischargedevices to thereby limit said current flow to a quiescent value, saidbiasing means including an impedance means located in said seriescircuit between said first and third discharge devices, said impedancemeans being of relatively low value compared to the internal impedanceof said second discharge device when the latter conducts said quiescentcurrent, whereby, when said first discharge device is cut off, thequiescent current through said series circuit is interrupted, the biason said second and third discharge devices thereby removed, and arelatively heavy amount of current, compared to said quiescent current,passes through said load and third tube, said impedance means ofrelatively low value permitting the bias on said second and thirddischarge devices rapidly to be overcome.

9. A pulse generating circuit comprising, in combination, first, secondand third discharge devices connected in series, in the order named, inanode-to-cathode relation, the cathode of said first discharge devicedefining one end of said series circuit and the anode of said thirddischarge device defining the other end of said series circuit; meansfor connecting said cathode end to a point of reference voltage; meansfor connecting said anode end to a point of voltage which is positivewith respect to said reference voltage and of sufficient amplitude tocause current flow through said series circuit; connection means for thecathode of said third discharge device for capacitively coupling saidcathode through a load to said point of reference voltage; and biasingmeans responsive to the current flow through said series circuit, whenin operation, for biasing said second and third discharge devices tothereby limit said current flow to a quiescent value, said biasing meansincluding impedance means located in said series circuit between saidfirst and second discharge devices, said impedance means being ofrelatively low value compared to the internal impedance of said seconddischarge device, when the latter conducts said quiescent current,whereby, when said first discharge device is cut oif, the quiescentcurrent through said series circuit is interrupted, the bias on saidsecond and third discharge devices thereby removed, and a relativelyheavy amount of current, compared to said quiescent current, passesthrough said load and third tube, said impedance means of relatively lowvalue permitting the bias on said second and third tubes rapidly to beovercome.

10. A pulse generating circuit as set forth in claim 9, said impedancemeans comprising a resistor having a value of resistance which isrelatively low compared to the internal resistance of said seconddischarge device when the latter conducts said quiescent current.

11. A pulse generating circuit as set forth in claim 10, said second andthird discharge devices comprising triodes, said biasing means beingconnected to apply bias to the control grids of said triodes.

12. A pulse generating circuit as set forth in claim 9, said second andthird discharge devices comprising pen- 7 8 codes, said biasing meansbeing connected to apply bias 2,488,567 Stodola Nov. 22, 1949 to thecontrol grids of said pentodes. 2,516,135 Moore July 25, 1950 2,520,174Slattery Aug. 29, 1950 References Cited in the file of this patent2,525,632 Anderson Oct. 10, 1950 UNITED STATES PATENTS 5 2,633,528Hutson Mar. 31, 1953 2,210,995 White Aug. 13, 1940 OTHER REFERENCES2,269,001 Blumlem 1942 Radiation Laboratory Series, pub. October 1,1948, pp. 2,282,340 Pleplow May 12, 1942 55 5 f VOL 2,310,342 Artzt Feb.9, 1943 2,446,802 Bell Aug. 10, 1948 10 2,449,998 Hansen Sept. 28, 1948

